1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor substrate having a semiconductor layer formed over an insulating layer and a method for manufacturing a semiconductor device.
Note that a semiconductor device refers to any device which can function by utilizing semiconductor characteristics in this specification. Electro-optical devices, semiconductor circuits, and electronic devices are all semiconductor devices.
2. Description of the Related Art
In recent years, integrated circuits using a silicon on insulator (SOI) substrate, instead of using a bulk silicon wafer, have been developed. By utilizing characteristics of a thin single crystal silicon layer formed over an insulating layer, a semiconductor layer of a transistor formed in the integrated circuit can be electrically separated from each other completely. Further, since the fully depleted transistors can be formed, a semiconductor integrated circuit with high added value such as high integration, high speed driving, and low power consumption can be realized.
As an SOI substrate, a SIMOX substrate and a bonded substrate are known. For example, for an SOI structure of a SIMOX substrate, oxygen ions are implanted into a single crystal silicon substrate, heat treatment at 1300° C. or higher is conducted to form a buried oxide (BOX) layer, so that a single crystal silicon thin film is formed on the surface.
As an SOI structure of a bonded substrate, two single crystal silicon substrates (a base substrate and a bond substrate) are bonded together with an oxide film interposed therebetween, and one of the two single crystal silicon substrates (the bond substrate) is thinned on its rear side (which is not a surface to be used for bonding), so that a single crystal silicon thin film is formed. There is proposed Smart-Cut (registered trademark) employing hydrogen ion implantation (e.g., Reference 1: Japanese Published Patent Application No. H5-211128), because it is difficult to form a uniform and single crystal silicon thin film by grinding and polishing.